The results of single and multiple pulse damage studies at 10.6, 1.06, and 0.532 um in diamond-turned bulk Cu and diamond-turned electro-deposits of Ag on Cu are presented. The single pulse damage threshold decreases or remains constant with increasing spot size, as previously reported. On the other hand, the multiple pulse threshold increases with increasing spot size. The difference in their behavior suggests that the two phenomena are the result of different mechanisms. Localized surface defects and impurities appear to be responsible for single pulse damage, while for multiple pulse damage a model is proposed based on the cumulative effect of plastic deformation induced by thermal stresses.